Client-side INSERT …​ SELECT, UPDATE, DELETE, MERGE and UPDATE OR INSERT queries containing the RETURNING clause may now return multiple records instead of raising error “multiple rows in singleton select” as it happened before.

These queries are now described as isc_info_sql_stmt_select during preparation, while in previous versions they were described as isc_info_sql_stmt_exec_procedure.

Singleton INSERT … VALUES statements, as well as positioned UPDATE and DELETE statements (i.e. the ones containing the WHERE CURRENT OF clause) preserve the existing behaviour, being described as isc_info_sql_stmt_exec_procedure. They also preserve the ability of being executed within a single protocol roundtrip to the server.